Telephone system



Jan. 19, 1932.

R. G. DIXON TELEPHONE SYSTEM Filed Aug. 51, 1931 2 Sheets-Sheet l W); D5 Rginald Erifii'th Dixon Jan. 19, 1932; R. G. DIXON TELEPHONE SYSTEM Filed Aug. 51. 1931 2 Sheets-Sheet 2 him-J5? Reginald Erififl'h Dix-mu Patented Jan. 19, 1932 warren sra rss rarest Price REGINALD GRIFFITH DIXON, OF LONDON, ENGLAND,

ASSIGNOR T0 SIEMENS BROTHERS & COMPANY LIMITED, 01? LONDON, ENGLAND TELEPHONE SYSTEM Application filed August 31, 1931, Serial No Thepresent invention relates to improved call finding arrangements in automatlc and semi-automatic telephone systems and has 1n View economy of space and cost and the re--- duction of the time required to find a line in a large group of lines. By call finder 1s meant that class of'switch which hunts for a marked contact in its banks whether the con-' nections to its banks are subscriber's lines 01' connections to other switches or circuits.

In systems in which a call finder gives access to a group selector or other circuit, the selector or other circuit having a relay conuected'to it and operable over: the wipers of the call finder, vided to prevent operation of the relay as the wipers of the call finder in searchingfor a calling line pass over busy lines. This operation is usually prevented by including in the circuit contacts of a relay operated only. when a calling line is found and the er has come to rest.

According to one feature of the present invention call finding arrai'igements are provided in which a call finder has no relay individual to but is controlled by apparatus available in common to a number of call iii ers serving the samegroup of incoming lines. 'The apparatus available in common to a group of call finders includes the controlling apparatus', e. g. relays, necessary for call findcarrying out the sequence of operations required and means for associating the controlling apparatus with the call finder'to be controlled. i

iiccording to another feature of the invention a switching device comprises a number of permanenty associated switches of which any one can perform a primary switching operation and one of the other switches not used for the primary switching operation concerned can be used for a secondary switching operation to make the operation of the first switch effective.

The switching device may be a call finder in which case incoming lines would be connected to the permanently associated switches which as a whole comprise a-call finder and one of the switches searches for a line when it assumes a calling condition, another switch 7 arrangements must be pro-' nected to the test 'fore searching for a calling 560,259, and in Great Britain m 26, 1930;

then being stepped to a predetermined position to conne ct the-line found by the first switch to the outlet from the call finder.

A roup of lines is multiplied over the call finders of a group and all the searching C3 switches of a call finder are adapted to search for calling lines but only that switch having access to a subgroup of lines con taining a callingline' is set in motion to search for it. 7 i 59 The outlet from a call finder is connected to bank contacts in the searching switches and corresponding wipers of each of the searching switches comprising a call finder are connected together but not to the outlet. As regards the test wipers these are concircuit in the common controlling apparatus. I v

Since only two of the searchingswitches comprising a call finder are required to be in use at the same time, the connections of the outlet need be made only in the banks of two searching switches and a single Contact in each switch bank suflices for the purpose. Certain other contacts of theseswitches may be allotted to the control of the call finder, the remaining contacts being connected to incoming lines.

The call finders need not return to a normal position after use but may remain with their wipers on the contacts onrwhich they were last used, a call finder when required for use being first restored to a starting position beline.

For the association of the common controlling apparatus with the call finders of a group a hunting switch maybe employed, the bank contacts being connected to call finders of agroup and it may be arranged that this switch always stands with its wipers on contacts connected to a free call finder.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings. In the drawings Fig. 1 Shows a subscribers line circuit, Fig. 2 a call finder and Fig.3 controlling apparatus common to a number of call finders and connectable thereto over an assigner.

The line circuit shown in Fig. 1 is connected at a distributing frame to the subconnects earth over contact 704: from the test wire and connects it to start wire 8 for starting a finder in search of the calling line. hen the line is found by a finder cut-elf relay K operates to earth connected over the test wiper of the call finder but the resistance of the circuit is too high to permit operation of the meter M which is operated at a later stage by increasing the current over wire in known manner. When relay.K operates it connects itself to the test wire at contact 7&1 independently of contact 71 and at contact 704 disconnects earth from the start wire 5. Relay L is released at contacts 702 and 703.

When a call is made over a final selector and wires FS to the subscriber connected to wires S'L relay K operates in the test circuit in the usual manner and disconnects relay L, contact 701 extending the earth over the final selector test wiper to the test wire in the call finder multiple to mark the line engaged therein.

Disconnection of earth from wire 0 releases relay K at the end of a conversation and the circuit then becomes free.

A call finder is shown in Fig. 2 and comprises 4 single motion searching switches each having 4 wipers and corresponding banks of 7 contacts.

A number of call finders operate on the same multiple and the lines in the multiple are divided into four sub-groups and as regards one finder one sub-group is connected in the banks of the switch represented by magnet AM and wipers AA, AB, AC, AH, a second subrgroup is connected in the banks of the switch represented by magnet BM and wipers BA, BB,BC, BH and the third and fourth sub-groups are connected in the banks of switches represented by magnet CM and wipers CACH and magnet DM and wipers DA-DH respectively.

As regards the line and test wire banks of a finder the first contacts are starting positi ons and are not connected, the switches having no normal position as after use they remain on the contacts on which they were last set. The second bank contacts in the corresponding banks of switches AM and BM are connected together and to one wire of the link to a succeeding switch which may be a nonnumerical switch or a numerical selector.

The third bank contacts in these two switches are disconnected and the fourth and remaining contacts are connected to lines in the mul- 7 tiple. As regards switches CM and-11M t e second and subsequent bank contacts are con nected to lines in the multiple. For ease in understanding these connections the first line in the multiple is indicated by reference letters, the letters ac, ab and ac designating the first line connected to switch AM and 72a, ca, 67a, the a wires of the first lines in the switches BM, CM and DM. The other lines are connected to the succeeding contacts in a similar manner.

The corresponding wipers of each switch are connected together and in the case of the test wipers they are connected over the wire T to the controlling equipment.

As regards the homing banks All-DH the first contacts in each bank are connected individually to contacts in banks of an assigner in the control equipment. The second contacts in the banks of wipers AH and BH are connected together and to wire X connected in another bank in the assigner, the third contacts in the last mentioned banks are connected together and to another bank in the assigner, and the fourth and subsequent contacts are commoned and connected to the second and subsequent commoned contacts in the banks of wipers CH and DH and to a further bank in the assigner. .The reference letters adjacent to the wires leaving the bottom of this figure correspond to the wipers of the assigner in the banks of which the wires are connected. Each switch magnet is provided with a self interrupting contact designated am, m, cm, (7777.. There is no relay individual to a call finder.

In Fig. 3 the controlling circuit is provided with an assigner having a magnet ADM and 8' wipers and banks of contacts indicated at T, .Y, Z, X, A, B, C, D. The assigner gives the controlling circuit access to a number of finders. Relays A, B, C, D, on the left of the figure are starting relays, one for the lines of each sub-group, the starting wires 8 of individual lines being connected in common to a group start relay.

In describing the operations concerned with the finding of a calling line it will be assumed that the assigner is resting with its wipers in engagement with contacts connected to a free call finder, that shown in Fig. 2; there will therefore be no earth connected to wire T (Fig. 2).

If now a call is made the start relay of the sub-group in which the calling line is connected is operated from earth over contacts 704 and 72 in the calling line circuit and the switches of the assigned finder which are off normal are first returned to normal after which the switch in the banks of which the calling line is connected is started in search of the calling line. This found, another switch of the finder, either switch AM or IBM is stepped to its second contacts to complete a connection from the calling line to the link to the succeeding switch. If the calling line leasing relay circuit is closed from of the switch last left is in the sub-group connected to switch AM then switch BM is stepped to its second con tacts to extend the connection to wires a, Z), 0, but if the calling line is in a group connected to any of the other switches then switch AM is employed for the extension of the connection. Switches CM and DM therefore need not be provided with the special connections to their 3rd and lth bank contacts and these contacts can be connected to lines.

i It will be assumed that a line in the subgroup connected to switch AM is calling. Relay A is consequently operated over the start wire 8 and at contact a1 short circuits its high resistance winding (1) to bring the point connected to contacts $84 to substantially earth potential to prevent operation of another starting relay. Contact a3 closes a circuit for slow releasing relay R over contact t3 and contact a l prepares a circuit for relay T. v consequent on operation of relays B, C, or D. Relay R operates and at contact r3 closes a circuit for relay T in series with magnet ADM. Belay T operatesand closes a holding circuit for itself at contact t1 independently of relay R. Contact 63 closes a circuit over contact T1 for winding (I) of slow re- P which operates and contact 322 operates slow releasing relay Q. Relays R, T and P being operated a circuit is closed from earth over contacts t4, 1293 low resistance winding (II) of relay P, contact 1'2 wiper X second contact in the bank of the switch AM or BM depending on which was last left in the switch through position, homing wiper, self interrupting contacts and switch mag net to battery. Assume it to be the switch AM and'that the switch BM was left in connection with a line contact. Magnet AM then operates and steps its wipers to the 3rd contacts. About this time relay R releases due to its circuit being opened at contact #3 and contact r2 falls back so that before relay P releases due to the opening of contact 1 1 a circuit is closed over its winding (II) contact 12, wiper Y commoned contacts in the bank in. contact with a line and assumed to be the switch BM, wiper BH and contact 6m for magnet BM. The magnet operates and steps switch BM rapidly to the first contacts or starting position, on reaching which no circuit remains for relay P and this relay after a brief interval releases. Consequent on the falling back of contact 773 earth is connected over contacts 2 4, p3, g2, wiper Z, 3rd contact in bankof wiper AH to magnet AM which thereupon operates and steps its wipers to the 4th contacts which are commoned to the remaining contacts in the homing bank and to wire Y.

Before relay Q has had time to release a earth over contacts f4, 91, winding (II) of relay P, contact 72, wire. Y to magnet AM. Magnet AM and now having its'wipers resting Similar circuits would be closed which in turn releases relay P operate and switch AM is stepped rapidly to its starting position on reaching which the circuit is opened and relay P releases. The release of relay P opens the circuit of relay Q releasing it thereby closing a circuit for relay S over contacts rel, 92,123, 254. Relay S operates and at contact 83 connects earth over contact a2, wiper A first bank contact and wiper AH to magnet AM which operates and steps its wipers to the second bank contacts.

Ingeneral, contact 83 connects earth to the magnet of the switch in the banks of which the calling line' is connected. Switch AM on the second contact a circuit is closed over magnet AM, and wiper X, contacts a5 and s1 and the switch is stepped to its 3rd contacts. Contact L5 in parallel with a5 provides for similar stepping of switch BM for a calling line connected to its banks. In the case of switches CM and DM the second contact is a line contact and search for a calling line. starts immediately as will be seen later. With its wipers on the 3rd contactsa circuit is closed for magnet AM over wiper Z, contacts 84, a5 and s1 and the switch steps to its fourth contacts connected to wire Y. RelayX which is of high resistance now operates in series withmagnet AM, the latter not operatin g in this circuit, and at contact [01 operates relay Y which holds over contacts 1 1 and t3. Contact g2 disconnects relay X and connects magnet AM over wiper contact $82, wiper T to the test wipers of the call finder thence over wiper AC and wire (to of the first line. If this ?is'not a calling line earth will be connected to it over contacts 704 and Z2 and magnet AM operates and steps the switch over contacts of non-calling and busy lines which are earthed in the test bank until a calling line denoted by battery potential on the test bank contact is reached whereupon stepping ceases and a circuit is closed over relay K, the test bank wiper T, contact t2, winding (I) of relay TS, contact 3 3 to earth. Relay TS operates and closes a holding circuit for itself over its winding (II), contacts 1581' and 81 and at con-- tact ts2short circuits its winding (I) and connectsearth directly over wire T and the test wiper AC to mark the line engaged. Contact 2583 releases relay T, contacts Z84 opens the common circuits for the start relays and contact ts5 connects earth over contact a6 and wiper B for magnet BM which steps its wipers to the second contacts. Meanwhile relay K operates, releases relay L and opens the circuit over the wire 8 individual to the calling line. before the start relay releases relay R reoperates and at contact 14 releases relay S relay TS. Relay R releases shortly after.

V Consequent on the setting of switch BM contact and wiper.

On the release of relay T and r switch which stood in the on its second contacts the calling line is switched through over wipers AA, AB, AC and BA, BB, BC to wires a, Z) and c and a relay in the switch connected to these wires operates and effects the connection of earth to wire 0 for holding the connection. This earth is extended also over wiper BC, wire T, wiper T, contacts '2 and 7583 to magnet ADM which operates and by interrupting this circuit at contact arlm steps the assigner over contacts connected to other busy finders until contacts connected to a free finder are reached. There is now no earth over wiper T and the assigner comes to rest.

If the calling line is connected in the banks of switch CM or DM the operation of this switch from the starting position is similar to that described for switch AM except that on reaching its second contacts a circuit is closed over wire Y for relay X, relay S being operated, and relays X and Y operate the latter connecting the switch magnet over wiper T and the test wiper of the switch concerned to the first line in the banks of the latter and search for the calling line proceeds forthwith.

If switch CM or DM is used in a connection then the next time the call finder is taken into use and on the release of relay R attcr switch AM has been stepped from the switch through position, i. e. the 2nd contacts to the 3rd contacts, earth over winding (II) of relay P is connected over contact 12 and wiper Y to magnet CM or Dm. as the case may be, and the switch is rotated to its starting position, i. e. 1st contacts.

Return to this position of switch AM then follows in the manner previously described.

It will be noted that relay P when oper ated closes contact 71 in parallel with contacts of the start relays in the circuit of relay T. Should a subscriber clear before the finder has been restored to its starting position relay T will continue to hold until the switch through position on the last conversation has been stepped to its third. contacts and the switch which was in connection with the line has been stopped to its starting position. At this stage relay P releases and releases relay T. hen next the finder is taken into use relays T. P and Q operate but as there is no con nection over wiper X relay P releases and closes the circuit over wipers Z for the switch left standing on its 3rd contacts due to the action above referred to. This switch is then stepped to its starting position in the manner previously described.

hat I claim as new and desire to secure by Letters Patent is:

1. In a telephone system, and a third line, a first and a second switch, permanent connections connecting said switches together, means for connecting said first and third lines together over said pera first, a second,

inanent connections by first operating said first switch to said first line and then operating said sec-0nd switch to said third line, and means for connecting said second and third lines together over said permanent connections by first operating said second switch to said second line and then operating said first switch to said third line.

2. In a telephone system, a first group of lines, a second group of lines. a trunk linega 75 first switch having access to said first group of lines and said trunk line, a second switch having access to said second group of lines and said trunk lines, permanent connections connecting said switches together, means tori connecting any one of said first group lines and said trunk line together over said permanent connectionsby first operating said first switch to one of said first group lines and then operating said second switch to said 8 trunk line, and means for connecting any one of said second group lines and said trunk line over said permanent connections by first operating the second switch to one of said second group lines and then operating the first switch to said trunk line.

3. In a telephone system, a first, a second, and a third line. a first and a second switch, wipers on said first switch having access to said first and third lines, wipers on said second switch havingaccess to said second and third lines, permanent connections connecting corresponding wipers of said switches together, means for operating the wipers of said switches, means for connecting the first and third lines together over said wipers and permanent connections by first operating the wipers of said first switch to said first line and then operating the wipers of the second switch to said third line, and means for coo nccting the second and third lines together over said wipers and permanent connections by first operating the wipers ot the second switch to said second line and then operating the wipers of the first switch to the third lineno 4-. In a telephone system. a pair of finders having their wipers connected together, a group of subscribers lines connected in the bank of one of said finders. a second group of subscribers lines connected in the bank (3 the other of said finders, a trunk line multipled in the banks of both said finders, and means for operating both of said switches to connect said trunk line with one of said subscribers lines.

5, In a telephone system, a pair of finders having their wipers connected together. a group ot subscribers lines connected in the bank of one of said finders, a second group of subscribers lines connected in the bank of the other of said finders. a trunk line multipled in the banks of both of said finders, and means common to said finders for independently operating first one finder and then the other finder to complete a connection be tween a subscribers line and said trunk line.

6. In a telephone system, a switching device comprising a plurality of switches permanently connected together, means for operatingany one of said switches in a primary switching operation to partially prepare a desired connection, and means responsive to said operated switch completing its primary switching operation for automatically operating a remaining one of said switches in a secondary switching operation to complete the said partially prepared connection by way of said first and second operated switches.

7 In a telephone system, a group of lines divided into subgroups, a trunk line, a finder individual to said trunk line but normally disconnected therefrom, said finder comprising a plurality of switches, permanent connections connecting said switches together, each switch having access to a dilferent subgroup of lines and said trunk line, means responsve to a call on one of said lines for operating only the switch having access thereto to find the calling line, and means responsive to said first switchfinding the calling line for operating a remaining one of said switches to said trunk line to connect said calling line to said trunk lineby way of said first and second operated switches and said permanent connections.

8. In a telephone system, a group of lines divided into subgroups, a plurality of trunk lines, a finder individual to'each trunk line but normally disconnected therefrom, each finder comprising a groupof switches, permanent connections connecting the grouped switches in each finder, corresponding switches in diiferent finders having access to the same subgroup of lines and non-corresponding switches in said finders having ac-v cess to different subgroups of lines, each group of switches in a finder having access to an individual one of said trunk lines, means common to sad finders for selecting an idle one of said finders, means common'to said finders responsive to a call on one of said lines for operating only the switch of the selected finder having access to the calling line to find such line, and means responsive to said operated switch finding the calling line for operating a remaining one of said switches in the selected finder to said trunk line to connect said calling line to said trunk line by way of said operated switches and their per-- manent connections.

9. In a telephone system, a pair of switches, each switch comprising only wipers, sets of bank contacts and a step 'Jing magnet for stepping the wipers over said bank contacts, a trunk line individual to said pair of switches and terminating in a set of bank contacts in each switch, incoming lines terminating in other sets of bank contacts in said switches, and means for operating the magnets of said switches to connect said trunk line with one of said incoming lines over a circuit including the wipers of said switches in series.

10. In a telephone system, a pair of switches, each switch comprising only wipers, sets of bank contacts, and a stepping magnet for stepping the wipers over said bank contacts, a trunk line individual to said pair of switches and terminating in a set of bank contacts in each switch, incoming lines terminating in other sets of bank contacts in said switches, means common to said switches for operating the stepping magnets of said switches to position the wipers of either one of said switches 011 a set of bank contacts of an incoming line and to thereafter position the wipers of the outer switch on the set of bank contacts terminating said trunk line, and multiple connections connecting corresponding wipers of the two switches for completing a circuit including the said incoming line, the wipers of said switches, and said trunk line in series.

In testimony whereof I aflix my signature.

REGINALD GRIFFITH DIXON. 

